Thanatophoric dysplasia and cloverleaf skull

Nine infants with thanatophoric dysplasia (TD) and cloverleaf skull (CS) are reported. Twenty‐two previously published CSTD cases are reviewed. These CSTD cases are compared to cases of TD without CS. U is concluded that there are two types of TD: type l, with curved femora and very flat vertebral bodies; and type 2, with straight femora and taller vertebral bodies. Consistent but subtle histopathological characteris‐tics differentiate the two types. Only a very few type l cases have CS, and the CS is mild. Almost all type 2 cases have severe CS.